This invention relates to the process of reacting isoparaffin and olefin compounds in the presence of an acid catalyst to form high octane gasoline alkylate product. Another aspect of this invention involves the recontacting of the alkylate reaction product, containing a quantity of organic fluoride reaction by-products, with relatively pure hydrogen fluoride catalyst in order to further convert the alkyl fluoride compounds to additional alkylate thereby increasing the process alkylate yield. A further aspect of this invention involves the arrangement of process equipment which allows for the use of a single vessel to serve a dual function of storing catalyst and of recontacting alkylate with alkylation catalyst, and further allows the draining of catalyst contained in certain process equipment by the sole use of gravitational motive force into a safe haven vessel.
In an alkylation process, high octane gasoline is produced by reacting in the presence of catalyst, preferably hydrogen fluoride, isoparaffins with olefins. Some of the alkylation reaction by-products are alkyl fluorides that are contaminants to the hydrocarbon products produced from an alkylation unit and, therefore, they must be removed. Various means have been used to remove alkyl fluorides one of which is the recontacting of the alkyl fluoride with high purity hydrogen fluoride to convert the alkyl fluoride compounds into additional high octane alkylate. This recontacting process is preferable over other alternative means of removing alkyl fluoride compounds in that a greater yield of high octane alkylate is produced and catalyst consumption is lowered. In a typical alkylation process unit, there is often provided a section in which the separated hydrocarbon phase of the reactor effluent is passed through an eductor device which draws hydrogen fluoride into the secondary inlet of the device and which mixes the two phases. The recontacted mixture passes to an acid recontacting vessel where the hydrocarbon phase and catalyst phase separate. During this recontacting step, the organic fluorides react to produce additional alkylate and release additional hydrogen fluoride.
Another concern with the alkylation process is the safe handling, transport, and storage of the alkylation catalyst. As is typically done, a catalyst storage vessel is provided where make-up catalyst is stored and in which the inventory of catalyst contained in the alkylation process may be inventoried when required. In emergency situations, there must be a means for quickly and safely transferring the process catalyst to safe containment within the storage vessel. Because of the hazardous nature of alkylation catalyst, any reduction in the number of separately contained volumes of catalyst held within the process can result in an improvement in operating safety of an alkylation